Vibratory conveyor



1968 w. c. BURGESS, JR 3,367,480

VIBRATORY CONVEYOR Filed Nov. 2, 1966 2 Sheets-Sheet 1 2 Q III llINVENTOR.

F ig, 2 9 WAEEEN C. 50126555 J2.

BYW/W TTOEA/Efi Feb. 6, 1968 w. c. BURGESS, JR

- VIBRATORY CONVEYOR 2 Sheets-Sheet 2 Filed Nov. 2, 1966 INVENTOR. 4VVAEEEN C. Bureeess J/a- ATTOENEYS, v

United States Patent Ofiice 3,357,480 Patented Feb. 6, 1968 VIBRATORYCONVEYOR Warren C. Burgess, Jr., 27018 Kennedy Ridge Road,

North Olmsted, Ohio 44070 Continuation-impart of application Ser. No.528,931, Feb. 21, 1966. This application Nov. 2, 1966, Ser. No. 600,320

4 Claims. (Cl. 198-220) ABSTRACT OF THE DISCLOSURE This inventionprovides a vibrator bowl type conveyor which is improved by providing apneumatic, free piston vibration-inducing device attached to the baseplate supporting the receptacle bowl and adapted to oscillate in theplane of the base plate.

This application is a continuation-in-part of my copending applicationSer. No. 528,931, filed Feb. 21, 1966, now abandoned.

This invention relates to vibratory conveyors, and more particularly tovibratory conveyors of the bowl type wherein articles or parts are fedfrom a supply thereof disposed within the bowl. Briefly, the inventionis characterized in that there is provided a pneumatic, free piston,vibrationinducing device which is mounted so as to oscillatehorizontally instead of verticall and in a plane which is the same as orsubstantially the same as the plane which includes the bottom of theconveyor receptacle.

Vibratory bowl type parts feeders are well known, and comprise a bowlhaving an upstanding wall and a trackway which proceeds upwardly fromthe bottom of the bowl around the periphery to an exit point at the toprim of the bowl. This bowl is mounted on a drive plate, or includesintegrally formed therewith a drive plate which is part of an energystorage and release system. The drive plate is mounted upon andsupported by a plurality of leaf type springs circumferentially disposedat uniform intervals about the axis of the bowl, and having their lowerextremities secured to a base which is desirably a massive unit. Thesesprings are disposed at a predetermined angle to the horizontal, e.g.,approximately 75. This assembly is typically driven by avibration-inducing device, for example, a pneumatic, vibration-inducingdevice having a free piston which oscillates in a cylindrical chamberalong the path which is coincident with the vertical axis of the bowl.This device is normally mounted on the bottom of the bowl or on thebottom of the drive plate to which the bowl is attached, as the case maybe.

When the device is constructed and operated as in the past, the actionmay become such that the bowl is elastically deformed by the action ofthe vibration-inducing device. Moreover, when eflort is made to feedfrom these conventional devices, it is found that feeding is greatlyaffected by changes in the loading of the parts within the bowl amongother factors. Under certain circumstances, it can be stopped entirely.It has been found that when operating with a vertically mounted impulseand inertia providing unit, the material or article to be conveyed fromthe bottom of the bowl is given a very substantial bounce or up and downmovement which can be considered as useless motion, and the component ofuseful energy is relatively low. Ideally, the operation of suchvibratory bowl feeders contemplates that all of the vibratory motionshould be transmitted along a path described by the vibrating end of thespring, rather than lost in vertical motion. Transmission along ahorizontal straight line is a close approximation to the ideal,especially with the impulse generating device located increasinglyradially remote from the center of vibration.

It has also been found that conventional variable frequency pneumaticdevices, as above described, have been limited as to load capacity. Inan 18" bowl, for example, a load capacity of from about 15 to about 20pounds was the upper limit before the ability of the device to feedbecame severly limited or ceased due to a rapid decrease or cessation ofthe ability of the impulse means to impart lateral movement to the partsor material being fed. It has now been found that, for the same capacitybowl, the vertical motion of the material may be held to a minimum and asubstantial part of the energy transmitted to the material convertedinto lateral motion. Loads in excess of 50 pounds have been utilizedwithout detrimental effect to the rate of feed. In order to achieve suchhigh loading, it is essential to utilize a high inertia system which canbest be provided with a free piston vibration inducing device.

Other vibration inducing devices, for example those of theelectromagnetic type or of the electric motor driven mechanical type,have been found to be unsatisfactory in high frequency, as may berequired to accommodate the change in natural frequency of the systemdue to the effect of the variation in the live load. With a pneumatic,free piston, vibration-inducing device, however, this device is easilytuned in respect of its frequency to the natural frequency of the entiresystem. The frequency of vibration of a pneumatic, vibration-inducingdevice is a function of the pressure of the air or gas being used todrive the piston.

A principal advantage of the improved apparatus of the present inventionis that the load carrying capacity of the device may be increasedsubstantially over the load carrying capacity of conventional vibratoryconveying devices. Certain embodiments of the present invention havewithstood vibrating loads of 240 pounds and more without any indicationthat the vibrating device had reached its maximum limitation, whereas,conventional devices of comparable size have ceased to function at amuch lower load of the order of one-fifth of this. It has also beenfound that by constructing the vibrating device utilizing principles ofoptimum geometric design as herein contemplated, there is a substantialimprovement in the amount of input energy which is converted into usefulwork. For example, with the apparatus of this invention employingoptimum geometric design with respect to the arrangement and location ofthe driving force, there may be obtained upwards of 97% conversion ofinput vibratory energy into useful conveying energy. Experience withdevices of the prior art has shown utilization of only a maximum ofabout 26% of the vibratory input energy being converted into usefulwork.

It has also been found that the consumption of gas, e.g., air, requiredto operate the conveyors of the present invention, is substantiallyimproved over that required of comparable devices not employ-ing optimumgeometric" design. For example, in a bowl type feeder having a bowldiameter of 15 inches, where air consumption has previously been about 4cubic feet for operation of such a device with a vertically mountedpneumatic, free piston, vibration-inducing device, it has now been foundthat 2 cubic feet or less of gas are sufficient to operate the samedevice of the same physical size at substantially the same feed rate,and with an increase in the load carrying capacity of the system.

The advantages of the present invention are achieved by mounting thepneumatic, free piston, vibration-inducing device so that the pistonwill oscillate along a line which is in the same general plane as thedrive plate, or the bottom of the bowl. In general, the mounting meansfor supporting the pneumatic, free piston, vibration-inducing device areintegral with the drive plate itself or the bowl itself. Mostimportantly, variation of the track speed of parts with changes in thebowl load has been materially reduced. Normally, there is a largeincrease in the rate of feeding with a decreasing load, with anaccompanying increase in bounce and instability of the parts as the bowlempties itself. The devices of the present invention, on the contrary,demonstrate a substantially constant feed rate during emptying of thebowl, and even more surprisingly at the time of refilling, when theloading is suddenly changed. This means a substantial increase inproduction with reliable performance.

The devices as herein contemplated are particularly useful as drivingmeans for vibratory conveyors and screens, particularly bowl type partsfeeders and screens wherein rapid, dependable movement of a particle oran article of manufacture along a predetermined arcuate pathway isdesired. The pathway may be curved, helical or spiral, horizontal orinclined, or any variation or combination thereof. Vibratory conveyingapparatus with which the advantages of the present invention can besecured include vibratoryv conveyors characterized by material hoppershaving an upstanding circular wall and having disposed about theinterior wall thereof a spiral track receding from a more central partof the bottom of the bowl upwardly, around and outwardly to the upperlip of the bowl.

In the annexed drawings:

FIGURE 1 is a side view of a vibratory conveyor of the bowl feeder type,constructed in accordance with this invention, with a portion of thehousing cut away to reveal the mounting of a receptacle on a driveplate, which is in turn mounted on springs, and which also reveals themounting of the vibratory-inducing device of the present invention onthe drive plate.

FIGURE 2 is a perspective view of a vibratory bowl conveyor drive unit,with the bowl removed, utilizing a free-piston, vibration-inducingdevice.

FIGURE 3 is a top view of the drive plate with projecting support armsand mounted on the support arms is a pneumatic free-piston,vibration-inducing device and drive plate member.

FIGURE 4 is a side elevational view of the pneumatic free-pistonvibration-inducing device and plate member.

Referring more particularly to the drawings, there is shown as thereceptacle, a feeder bowl 1. The feeder bowl 1 may be cast or fabricatedfrom any convenient material, one such material being a polyesterreinforced with glass fibers, others being aluminum or steel. The feederbowl 1 which is described in U.S. Patent No. 2,985,280, is convenientlyafiixed to a drive plate 2, such as by bolt 3. The plate 2 is supportedupon a plurality of flat springs 4, two of which are shown in FIGURE 1,each of those shown having an opposite counterpart not shown, making atotal of four fiat springs. This number is merely exemplary, and may bemore or less. For example, eight springs circumferentially and uniformlydisposed about the vertical axis at the bowl are shown in FIGURES 3 and4. The springs 4 are conveniently clamped to the plate 2 as by bolts 5,and the other end thereof to a base plate 6 as by bolts 5, through clamp7-7a. The plate 6 is, in turn, conveniently welded or otherwise securedto a massive base 9.

Also shown is a pneumatic, free-piston vibration-inducing device 10mounted to an extended support arm attached to the drive plate 2. Arm10b serves to stabilize the device. A vibration-inducing device of thefree-piston type is described in each of US. Patent Nos. 3,023,738 and2,985,280.

These free-piston, pneumatic vibration-inducing devices provide acontinuous deceleration and acceleration of the moving piston due to theentrapment and escape of gases, as distinct from that in an impactingtype of action. The power input in one direction of the piston is thesame as the power input in the opposite direction. When using this typeof a vibrator, the frequency can be varied in response to the gaspressure during operation. It is possible to operate at naturalfrequency and, thus, take advantage of the vast increase in performanceat this point, which performance falls rapidly away as one departs a fewcycles either way from natural frequency. The pneumatic free-pistondevices hereof are capable of immediate tuning to the natural frequencyof the system. Reference may be had to US. Patent No. 2,861,548 fordetails of such pneumatic vibration-inducing devices. These devices arecharacterized by a substantially square wave power profile as detailedin US. Patent No. 3,186,537.

As indicated above, there are usually four modified single member flatsprings 4, spaced 90 apart and equidistant from the axis of the bowl 1,although eight such springs as shown in FIGURES 3 and 4 may be used inlarger installations. The springs 4 are angularly disposed at about 60inclination to the base 6, although any angular disposition betweenabout 15 and about may be used. The purpose of the angular and circulardisposition is to provide that the effect of the spring members is notonly to return the bowl upwardly after being lowered, but also to exerta torque in a direction to throw the material counterclockwise (in theexample shown in FIGURE 1) along the ramp to the exit 12 of the bowl 1.Reversal of the direction of inclination of the springs will reverse thedirection of flow. The confined path of vibration or reciprocation inthis embodiment is curved and inclined, and may have a length varyingfrom about .01 inch to .6 inch in larger devices, depending on thedesired feed rate.

A suitable power control system is as found in Patent No. 3,023,738,dated Mar. 6, 1962, and which enables the adjustment of frequency ofvibration and amplitude of vibration substantially independently one ofthe other.

The ability to tune the frequency by regulation of gas pressure directedto the free piston by internal porting enables operation of the devicesat or near natural frequency, the point of greatest operatingefficiency. This control feature distinguishes the pneumatic free pistonvibration-inducing device from electromagnetic and electric motor drivenmechanical vibration-inducing devices, the frequency of vibration ofwhich is determined by that of the electric power source. The controldevice also protects the system from variations in power supply, whereasthe electrically operated systems are affected directly by changes involtage to the detriment of their feeding characteristics. Moreover, thepneumatic device has a square wave power profile which is particularlyadvantageous as distinct from the sine wave power profile whichcharacterizes the electromagnetic and mechanical vibrators.

As illustrated in the drawings, the vibration-inducing device issubstantially parallel to and in the same general plane as the platemember. Thus the vibration-inducing device oscillates in substantiallythe same general plane as the plate member to give the plate member ashaking motion; that is, the axis of the vibration-inducing device ispositioned on a line parallel to a tangent to a circle having its centerat a point equidistant from the springs and in the plane of the plate oran adjacent plane parallel thereto so as to apply a vibratory force tothe plate.

To illustrate the improved results obtainable over prior pneumaticallydriven bowl type parts feeders, the pneumatic vibration-inducing deviceor pneumatic drive means had a free piston having a 2 inch diameter. Thebowl was 35 inches in diameter and formed of .125 inch steel sheet. Themassive base was 30 inches by 30 inches by 4.5 inches steel. Eight glassfiber reinforced, 31 ply epxoy resin springs, 6 inches by 2 inches by0.25 inch, were mounted on a 30 slope to the vertical with their centerlines on a 12 inch diameter circle. The natural frequency of each systemtested was approximately 1650 cycles per minute. In the first test thevibration-inducing device was conventionally mounted so that the freepiston oscillated vertically below the drive plate and in the secondtest,

the same drive was mounted on a side arm extending laterally from thedrive plate so that the free piston oscillated horizontally inaccordance with the invention.

The results of these two tests were assembled and tabulated as follows:

Increase in efficiency of fecdi percent": Increase 111 speed, percent 1Very steady. 2 Measured speed divided by (frequency) (amplitude).

To illustrate the increase in the load carrying capac ity, the followingcomparative data is oiiered:

It has also been found that the plate member can have attched thereon apair of synchronized vibration-inducing device 180 apart. The loadcarrying capacity of such a unit is substantially improved over a onedrive unit.

Because of the improved configuration as herein contemplated, the driveangle (a) along the bowl edge is a minimum of 7 degrees with the averageangle for good feeding from 10 to 11 degrees. The drive angle forconventional vibratory devices is a minimum of 13 degrees and about 15degrees for good feeding action. The drive angle, which is the angle ofmovement of a point at the bowl perimeter, is a measure of the bounce orthe up and down movement of the moving material within the bowl. Thesmaller the angle the less energy expended in useless movement of thematerial. Also, the track within the bowl often has a selection typedevice incorporated into it so that as the material is advanced alongthe track it can be sorted as to properties. Thus, it can be seen thatthe more stable the material, the more accurate is the selection, andthe higher the quality of the selected material.

It has also been found that the diameter of the circle described by thespring centerlines is important in obtaining the optimum geometricconfiguration for a given bowl, drive, spring system, and base assembly.It has been found that the amplitude of vibration varies approximatelyinversely as the diameter of the spring center-lines, i.e., the diameterof the circle which is intersected by the centerline of each of theflat, leaf-type springs circumferentially disposed about the verticalaxis of the bowl. The parameter which is used for optimum design of aparts feeder bowl is the ratio of the bowl diameter to the springcenterline diameter. In a sidearm drive device, it has been found thatthis ratio is optimum at from about 1.9 to about 3.0. The bowl diameteris the overall diameter of the bowl at the upper lip. The springcenterline diameter is as described above.

In summary, the optimum geometric design parameter which yields optimumperformance over the broadest range of variation in weight in the bowlis achieved in accordance with the following, as compared toconventional vibratory parts feeder design parameters:

Item Conventional 0. GD.

Vibratory Mounting... Central and Vertical- Side and Horizontal.Eifective Drive Minimum plus 13 Minimum 7. Angle at Bowl Track Maximumplus 18 Maximum Unknown.

Sidewall For Good Action, 15. F111;) Good Action,

Spring Centerline 16 inches 12 inches.

Diameter (30 springs). Bowl diameter 35 inches 35 inches. Ratio of BowlSize of 2.2 2.9.

Spring Centerltne Diameter. Maximum Amplitude. .250 inch .300 inch.

What is claimed is:

1. In a vibratory bowl conveyor comprising a circular receptaclesupported upon a base plate, said base plate being resiliently mountedupon a plurality of inclined springs radially disposed about an axisnormal to and extending through the center of the bottom of the circularbowl and attached to a base member, the improvement which compriseslateral support means projecting laterally from said base plate, and apneumatic, free-piston vibration-inducing device radially disposed fromthe center of said bowl secured to the outer extremity of said laterallyprojecting support means, the free piston of said vibration-inducingdevice being positioned to oscillate substantially in the plane of saidbase plate.

2. A vibratory bowl conveyor comprising a circular bowl having a bottom,an upstanding annular wall, and an inclined spiral conveyor trackextending from the bottom upwardly around the annular wall, the trackprogressively receding from the center of the bottom of said bowl as thespiral conveyor track approaches the rim of the bowl, a base plate tosupport the receptacle, the base plate including a lateral support meansprojecting laterally from the plate, a pneumatic, free-pistonvibration-inducing device mounted on said laterally project ing supportmeans and radially disposed from the center of the bowl, the free pistonof said vibration-inducing device being adapted to oscillatesubstantially in the plane of the base plate along a line parallel to atangent to a circle having its center at a point equidistant from thesprings and in the plane of the plate, the base plate being resilientlymounted upon a plurality of inclined springs radially disposed about anaxis normal to and extending through the center of the bottom of thecircular bowl and at an angle to the plane of the base to support thebase and to guide the bowl along an arcuate path of movement, and thesprings being attached at one end portion to a massive base member.

3. The vibratory bowl conveyor of claim 2 wherein the support means is apair of spaced apart support arms, parallel to one another and adaptedto support the pneumatic, free-piston vibration-inducing device.

4. The vibratory bowl conveyor of claim 2 wherein the ratio of thediameter of the bowl to the spring centerline diameter is within therange of from 2.5 to 3.5.

References Cited UNITED STATES PATENTS 6/1931 Heymann l98-220 4/ 1962Burgess 198-220

